Bad Service with return of products

I bought some bra's for my mother at Ackermans Lambton on Monday, but they were to small. She took it back on Tuesday, they didn't have her size. She ask for the money back. They refuse to give her the cash back and told her that they need my card because I paid with my debit card. She went back on Wednesday with my card, they said they have reversed the money back into my account, but the money is not in my account. This is not the first time that I am having problems with Ackermans Lambton when want to return goods. The manager is of no help either.